US3165304A - Shaft kiln - Google Patents

Description

Jan. 12, 1965 A. M. TVERGAARD ETAL 3,165,304

SHAFT KILN Filed Jan. 14, 1963 3 Sheets-Sheet l INV EN TORS 446: M. TVEAGAAPD, ALBERT H. PACK, y WILL/AM W CAMPBELL 5.4434 1.54 T/ldM ATTORNEY A. M. TVERGAARD ETAL 3,165,304

Jan. 12, 1965 SHAFT KILN 3 Sheets-Sheet. 2

Filed Jan. 14, 1963 mammals 54494 LEJT/IJM Jan. 12, 1965 A. M. TVERGAARD ETAL 3,165,304

SHAFT KILN 3 Sheets-Sheet 3 Filed Jan. 14, 1963 LA ,L

United States Patent 3,165,304 SFAFT KILN Ange M. Tvergaard, Albert H. Pack, and William W.

Campbell, Ludington, Mich, and Earl Leatharn, Wesford, Pa., assignors to Harhison-Walker Refractories Company, Pittsburgh, Pa, a corporation of Pennsylvania Filed Jan. 14, 1963, Ser. No. 251,415 12 Claims. (Cl. 2263-29) This invention relates to the construction of shaft kilns for operation at very high temperatures. More particularly it relates to improved shaft kiln construction suitable for dead burning magnesite and the like.

The art of kiln construction is very old and the litera ture, particularly the patent literature, is replete with suggested constructions and methods of operation for kilns. One segment of the art of kiln construction or design relates to what is sometimes termed shaft kiln design. Shaft kilns are usually vertical kilns in which a charge of material 'to be treated is passed downwardly through the open top of the kiln in counter-current flow to an upwardly moving stream of hot gas. This type Previous shaft. kilns for dead burning dolomite. and magnesite have consisted of a refractory lined steel shell of the type disclosed in said co-pending application. The refractory lining was supported by a horizontally disposed annular steel plate which was in turn supported by beams welded to the steel shell. A stainless steel skirt was welded about the aperture through this annular plate and 7 extended downwardly therefrom to (l) confine the mateof kiln has been employed most frequently in the calcining of limestone. In calcining limestone it is. desired to drive off certain natural constituents to obtain a chemically reactive product. The chemical equation occurs in the I struct kilns for dead burning magnesite and dolomite because the required dead burning temperature for these materials is above about 3000 F. Some kilns, for dead burning'magnesite and dolomite, now operate between 4000 and 5000 F. The 4000 Filigure is more applicable to dolomite. V g

With the lower calcining temperature for limestone it has been possible to incorporate various modes of auxiliary flow directing apparatus interiorly of the kiln. These have included sequential burning stages, one under theother in a common kiln shell, which tended to assure that all of the charge passing through the kiln was heated to at least the desired disassociation temperature of cal cium carbonate. Various internal baffiing arrangements have been suggested to deflect gas flow and charge move ment to produce intimate admixing interiorly of the kiln. Others have suggested a plurality of juxtaposed ducts interiorly of a common shell as another means of assuring intimate association between the downwardly moving charge of limestone and the upwardly moving charge or hot gases. However, the foregoing arrangements are notsuited for the operation of a kiln above about 3000 F. because the temperatures involved are beyond the range of the normally used materials of construction. A particularly satisfactory design for the refractory lining of tubular shaft kilns of the type to which this invention relates is disclosed in co-pending U.S. patent application S.N. 203,659 filed July 19, 1962, now abandoned, owned by a common assignee. In operating kilns of the type disclosed in said co-pending application it has been found diflicult to cool the product uniformly at 0 near the bottom discharge.

rial being discharged from the bottom of the kiln and to (2) protect the adjacent metal structural members from the radiant heat of the discharging product.

This arrangement was not entirely satisfactory. The downwardly extending skirt was subject to extensive erosionbecause of contact with the hot discharging material. Further, the skirt was dificult to inspect for signs of damage, particularly when the kiln operation fluctuated and the product discharged at temperatures above 2000 F. Also, above 2000 F. the skirt deformed due to softening of the metal. Furthermore, the margin of safety against catastrophic failure of the kiln bottom due to very wide fluctuations in the operation of the kiln was not as great'as desired. In a kiln of this design, where the charge is supported by the discharge table only, with the table in turn held in place by the skirt, a rupture or even a large deformation of the skirt allows the charge to run off the edge of the table thus emptying the kiln into the bottom chamber. The 3000-4500" F. material thus discharged into the bottom half of the kiln can melt or otherwise cause irreparable damage to the bottom cone and the structural members which support the kiln.

Accordingly it is an object of this invention to provide improved construction for high temperature shaft kilns. It is another object of the invention to provideimproved shaft kiln construction suitable for deadburning materials above about 3000 F. It is a further specific object of the invention to provide improved construction for the lower end of a vertical shaft kiln suitable for dead burning refractory materials above about 3000" F.

Other objects, and further features and advantages of this invention. will become readily apparent to those skilled in the art from a study of the following detailed description with reference to the appended drawings. In these drawings:

FIG. 1 is a schematic side elevation in partial section of the bottom of a high temperature shaft kiln embodying the concepts of this invention; a

FIG. 2 is a view taken along the line 2-2 of FIG. 1; and

FIG. 3 is a view taken along the line 33 of FIG. 1.

Before describing the drawings in detail it should be understood they are but exemplary of construction embodying the concepts of our invention, and are given by way of explanation and not by way of limitation.

In FIG. 1 there is shown the bottom portion of a vertical kiln constructed according to this invention and which is capable of dead burning refractory material above about 3000 F. The kiln includes an upper inlet 8 and a bottom outlet 10 defined by the concentric relatively thin tubular outer shell 11 and the internal refractory lining 12. Refractory lining 12 is of substantial thickness and may be on the order of two or three feet as compared to the about /2 inch thickness for the shell 11. A burner 16 having a suitable valve 18 (FIG. 2) is positioned at the dead burning zone intermediate the ends of the kiln for obtaining temperatures of at least about 3000 F.

A plurality of curved bottom plates 20 are arranged to form an inwardly converging skirt of such dimensions as to contiguously abut and support the downwardly converging outer surface of the truncated bottom portion 13 of the refractory lining 12. The plates 20 have flanges 21 formed about their upper peripheries. The flanges time it reaches the combustion zone of the'kiln.

21 have a plurality of apertures formed therethrough adapted for cooperationwith bolts 122,:and apertures" formed through the shelllll, to support the plates 2%;

The other end 23 of each of the plates 26 is likewise apertured and arranged tohavethe upwardly extending car 24' of the retainer ring 25 bolted thereto. The ring 25 is arranged to contiguously abut andsupport the bottom face 26 of the conical portion of the lining. V

The converging portion 13 of the lining is characterized as a generally downwardly converging truncated elliptical come 13 having a tubularpassageof substantially uniform cross-section passing therethrough. The crosssectional configurationof the passagethroug'h the truncated elliptical cone section of the lining is substantially f the same as the cross-sectional configurationof the passage through the refractory lining immediately thereabove. I

It is preferred that the slopeof the downward con vergence or" the outer surface of the bottom of the lining be on the. order of. about 30 relative to the vertical.- However, this angle is variable as long as a smalllip remains at thebottom to. form the surface 26 in order to provide better support for the;lining. Alternatively,- a

plurality ioflugs. (not shownl'may be driven through plates 2t) into the cone portion 13 to provide extra support; Of course, a retainer ring and lugs may be used. In a preferred embodiment, the outer shell 11 extends a distance beyond the bottom of the refractory lining and Y then converges to form a chamber '27 below'plates 2i having a bottom outlet 28.

In .a preferred construction an air'inanifold' 29 is positioned below the discharge tabledil. Afdrag bar' dl isv positioned between the retainingring 25 and the upper surfaceof the discharge table 39." Opening through the discharge table area series of apertures interconnected with theymanifol'd 29 through a plurality of separate con' duitsrttl' (see FIG. 3); A bathe 43, beneath each aperture'fifliprevents briquettes 44 from filling the manifold.

Each of the conduits it? has a suitable valvedzl included therein. Bysuitable manipulation of the valves tithe cross-sectional configuration of airbeingintroduccd into the bottom of the kiln may be, adjusted to oil-set horizontal non-uniformity "in the product temperatures.

By introducing air "through a manifold arrangement.

such as shown in the drawings, it has been found that the average temperature'of briquettes' being discharged g from the bottom of the shaftkiln'can be reduced by as i In addition to better cooling of the much as 500? F. briquettes, the air is more. uniformly preheated by the campaign production was increased by about20 percent over construction without the manifold. Also, the prod uctwas more uniform.

With the downwardly converging, cross-s'ectionally refractory lining, there is provided greater protection for In one;

-'converging refractory lining. a

.3. In a kiln of the type described in claiml, separate 7 means positioned within each manifold compartment to preventcharge material from entering said compartments,

shell below the conical skirtffitl for even closer inspection of the interior of the "bOllOl'll of the kiln;

Wehavealso discovered that .less' expansion occurs in the metal parts in the lower portion of the kiln with our construction; This. is 'Tp robablyl' due to, the additional insulation effect provided by the converging portion of the lining.

Having thus described the invention in detail and with sufiicient particularity as to enable those skilled in the art'to practice it what we desire to have protectedby' Letters Patent-is ,set forth in the following claims'i 1. In a vertical kiln of the type cap'abl e'of dead'burm ing refractory material above about 3090? 'F.,.said kiln including means defining an "upper inlet and af bottom outlet, means positioned at a deadburning zone located intermediate the endsfof the kiln arranged to obtain a temperature of at least about 3000*. Fin said dead burning'zone, a tubular outer shell having'a relativelyrthick refractory"lining contiguously positioned there-within to define-a vertical passage, means arranged-to continuously pass a gas stream in through the bottom outletandthe' passa'gein upwardly moving countercurrent flow; to a downwardly moving chargeof matcrialto be'dead burned, a dischargetable spaced beneath the kiln outlet,-means positioned above theftable and beneath the kiln ,outlet' arranged to assure dischargeof material from said table,

the bottom of said refractory'lining, a substantialldistance 1 below the dead burning. zone of the kiln, beingchare acterized as a .downwardlyconverging truncated cone "having a tubularpassage of substantially uniform cross} section passing therethroug'h, plate Qmeans, said'p late meanscarried by the :kiln in positiontol contiguous'ly abut and supper 'ofthe refractory lining;

't the exteriordownwardly converging surface 2. In a vertical kiln ofthe type Ca tesi n buming refractory material above about 3000" F.,xsaid kiln.

including means defiining .an upper-inlet-and a bottom outlet, means positioned at a dead ,burning'zone located intermediate the endsfof the kiin'a'rranged'to obtain a temperature of at least'about 30O0" F. in said dead burn- .re'fractoryi, lining .contiguously. positioned there within to define a verticalpassage, a discharge. table. spaced beneath {the kiln outlet, a plurality bf. apertures fo rmed through, the discharge table, Imanifold means including a plu rality of separate compartments, said manifold ,mcans supported-beneath thedischargetableso that each one of its. compa'rtmentsfopensthroughoneiof the discharge table apertures, means arrangedto separately deliver air 'to each "of the separate, compartments. toltliereby pass 7 air through the apertures in the; discharge table and through the'kiln passage-in upwardlymoving countercurrent flow to a downwardly .moving charge .of material tobe dead burned, the bottom of said refractory lining,

J a-substantial distance below the deadburning zone of elongated, elliptical configuration for the bottom of the the sheet steel adjacent the bottom of the kiln. Further- Y Y of metal shell Ill in order to determine the condition of the' support structure for the refractory lining.

desired, ports .(not shown) may be formedthrough'the the kiln, being characterized. a'sia downwardly converg- .ing truncated cone having a tubular passage ofsubstantially uniform cross-sectionpassing therethrough, means carried by the kiln arranged to'supportsaid downwardly 4. In a kiln of'the'type described in claim 2, adjust able means. carried by said manifold means 'arrangedto adjust the air flow t0 the separate compartments of the a .manifold.

5. In, a vertical kiln of the typecapable ofdead burning reftactoryrnatierial above about 3000" R, saidkiln including means defining an upper inlet and -a bottorn out- 1et,"means positionedat a dead burning zone located intermediate the ends of the kiln arranged to'obtain a tern V perature of at least about 30OQ- F. in said dead burning zone, a tubular outer-"shellhavinga relatively thick re.-

fractory lining contiguously positioned there within to define a vertical passage, a discharge table spaced beneath the kiln outlet, a plurality of apertures formed through the discharge table, manifold means including a plurality of separate compartments, said manifold means supported beneath the discharge table so that each one of its compartments opens to the discharge table apertures, means arranged to deliver air to each of the separate compartments to thereby pass a stream of air upwardly through the discharge table to the kiln passage in upwardly moving countercurrent flow to a downwardly moving charge of material to be dead burned, the bottom of said refractory lining, a substantial distance below the dead burning zone of the kiln, being characterized as a downwardly converging truncated cone having a tubular passage of substantially uniform cross-section passing therethrough, means carried by the kiln arranged to support said downwardly converging refractory lining, said outer metal shell extending a substantial distance below the discharge table to form an enclosed chamber there beneath, a charge outlet from said chamer, an outlet conduit opening through said chamber at a position above the outlet therefrom whereby excess air entering through said manifold means may be vented.

6. In a vertical kiln of the type capable of dead burning refractory material above about 3000 B, said kiln including means defining an upper inlet and a bottom outlet, means positioned at a dead burning zone located intermediate the ends of the kiln arranged to obtain a temperature of at least about 3000" F. in said dead burning zone, a tubular outer shell having a relatively thick refractory lining cont-i uously positioned there within to define a vertical passage, a discharge table spaced beneath the kiln outlet, a plurality of apertures formed through the discharge table, manifold means including a plurality of separate compartments, said manifold means supported beneath the discharge table so that its compartments open through the discharge table apertures, means arranged to separately deliver air to each of the separate compartments to thereby pass air through the apertures in the discharge table and through the kiln passage in upwardly moving countercurrent flow to a downwardly moving charge of material to be dead burned, the bottom of said refractory lining, a substantial distance below the dead burning zone of the kiln, being characterized as a downwardly converging truncated cone having a tubular passage of substantially uniform crosssection passing therethrough, means carried by the kiln arranged to support said downwardly converging refractory lining.

7. In a vertical kiln of the type capable of dead burning refractory material above about 3000 F., said kiln including means defining an upper inlet and a bottom outlet, means positioned at a dead burning zone located intermediate the ends of the kiln arranged to obtain a temperature of at least about 3000 F. in said dead burning zone, a tubular outer shell having a relatively thick refractory lining contiguously positioned there within to define a vertical passage, a discharge table spaced beneath the kiln outlet, a plurality of apertures formed through the discharge table, manifold means including a plurality of separate compartments, said manifold means supported beneath the discharge table so that each one of its compartments opens through one of the discharge table apertures, means arranged to separately deliver air to each of the separate compartments to thereby pass air through the apertures in the discharge table and through the kiln passage in upwardly moving countercurrent flow to a downwardly moving charge of material to be dead burned.

8. In a vertical kiln of the type described in claim 1, said plate means consisting of a plurality of metal plates, said plates atiixed at one end to the interior surface of the outer metal shell in position to contiguously abut and support the exterior downwardly converging surface of the refractory lining.

9. In a vertical kiln of the type described in claim 1, there being a substantially flat surface about the bottom of the refractory lining forming the outlet, said plate means consisting of a plurality of metal plates, said plates afiixed at one end to the interior surface of the outer metal shell in position to contiguously abut and support the exterior downwardly converging surface of the refractory lining, and retainer ring means carried by the other end of said plates contiguously abutting said substantially flat surface about the bottom outlet of said refractory lining.

10. In a kiln of the type described in claim 7, separate means positioned within with each of the separate compartments to prevent charge material from entering said compartments.

11. In a kiln of the type described in claim 7, adjustable means carried by said manifold means arranged to separately adjust the air flow to the separate compartments of the manifold.

12. In a vertical kiln of the type capable of dead burning refractory material above about 3000 F., said kiln including means defining an upper inlet and a bottom outlet, means positioned at a dead burning zone located intermediate the ends of the kiln arranged to obtain a temperature of at least about 3000 F. in said dead burning zone, a tubular outer shell having a relatively thick refractory lining contiguously positioned therein to define a vertical passage, a discharge table spaced beneath the kiln outlet, a plurality of apertures formed through the discharge table, manifold means including a plurality of separate compartments, said manifold means supported beneath the discharge table so that at least one of its compartments opens through each one of the discharge table apertures, means arranged to deliver air to each of the separate compartments to thereby pass a stream of air upwardly through the discharge table to the kiln passage in upwardly moving countercurrent flow to a downwardly moving charge of material to be dead burned, shell means forming a chamber positioned about the bottom of said kiln arranged to provide for collection of dead burned material discharging from said table, means forming an outlet conduit opening from said shell means, and means forming a dead burned material discharge outlet opening from said chamber at a position below said outlet conduit, said outlet conduit normally open to the atmosphere whereby excess air entering through said manifold means may be vented to the atmosphere.

References Cited by the Examiner UNITED STATES PATENTS 484,999 10/92 Curtis et al 50-160 X 696,420 3/02 Dougherty 2l4l8 704,806 8/02 Iamieson 50113 1,586,318 5/26 Mabee 263-29 2,628,829 2/53 Ruiz 263-29 2,938,782 5/60 Toulmin 266-25 X 2,951,756 9/60 Cavanagh 26625 X 3,003,756 10/ 61 Steffensen 263--29 FOREIGN PATENTS 602,653 12/25 France.

CHARLES SUKALO, Primary Examiner.

JOHN J. CAMBY, Examiner.

Claims (1)

1. 7. IN A VERTICAL KILN OF THE TYPE CAPABLE OF DEAD BURNING REFRACTORY MATERIAL ABOVE ABOUT 3000* F., SAID KILN INCLUDING MEANS DEFINING AN UPPER INLET AND A BOTTOM OUTLET, MEANS POSITIONED AT A DEAD BURNING ZONE LOCATED INTERMEDIATE THE ENDS OF THE KILN ARRANGED TO OBTAIN A TEMPERATURE OF AT LEAST ABOUT 3000* C. IN SAID DEAD BURNING ZONE, A TUBULAR OUTER SHELL HAVING A RELATIVELY THICK REFRACTORY LINING CONTIGUOUSLY POSITIONED THERE WITHIN TO DEFINE A VERTICAL PASSAGE, A DISCHARGE TABLE SPACED BENEATH THE KILN, OUTLET, A PLURALITY OF APERTURES FORMED THROUGH THE DISCHARGE TABLE, MANIFOLD MEANS INCLUDING A PLURALITY OF SEPARATE COMPARTMENTS, SAID MANIFOLD MEANS SUPPORTED BENEATH THE DISCHARGE TABLE SO THAT EACH ONE

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